Ionic Liquids Containing Guanidinium Cations

ABSTRACT

The present invention relates to salts having guanidinium cations, to processes for the preparation thereof, and to the use thereof as ionic liquids.

The present invention relates to salts containing guanidinium cations and various anions, to processes for the preparation of these salts, and to the use thereof as ionic liquids.

Ionic liquids or liquid salts are ionic species which consist of an organic cation and a generally inorganic anion. They do not contain neutral molecules and usually have melting points below 373 K. The prior art discloses a multiplicity of compounds which are used as ionic liquids. In particular, they are also the subject-matter of a series of patents and patent applications. Thus, solvent-free ionic liquids were disclosed for the first time by Hurley and Wier in a series of US patents (U.S. Pat. Nos. 2,446,331, 2,446,339 and 2,446,350). These “salts which are molten at room temperature” were based on AlCl₃ and a multiplicity of n-alkylpyridinium halides.

In recent years, some review articles on this topic have been published (R. Sheldon “Catalytic reactions in ionic liquids”, Chem. Commun., 2001, 2399-2407; M. J. Earle, K. R. Seddon “Ionic liquids. Green solvent for the future”, Pure Appl. Chem., 72 (2000), 1391-1398; P. Wasserscheid, W. Keim “Ionic liquids—novel solutions for transition-metal catalysis”, Angew. Chem., 112 (2000), 3926-3945; T. Welton “Room temperature ionic liquids. Solvents for synthesis and catalysis”, Chem. Rev., 92 (1999), 2071-2083; R. Hagiwara, Ya. Ito “Room temperature ionic liquids of alkylimidazolium cations and fluoroanions”, Journal of Fluorine Chem., 105 (2000), 221-227).

The properties of ionic liquids, for example melting point, thermal and electrochemical stability and viscosity, are greatly influenced by the nature of the anion. By contrast, the polarity and hydrophilicity or lipophilicity can be varied through a suitable choice of the cation/anion pair.

There is therefore a demand for novel ionic liquids having varied properties which facilitate additional possibilities regarding their use.

The object of the present invention is to provide novel stable salt-like compounds of low viscosity which can be used as ionic liquids, and a process for the preparation thereof.

This object is achieved by the provision of salts having guanidinium cations in which the positive charge is delocalised over a plurality of nitrogen atoms, in combination with selected anions in accordance with claim 1.

A publication by Peter J. Stang et al., J. Amer. Chem. Soc. 1981, 103 (16), 4837-4845, discloses the compound 1,3-dimethyl-2-diethylaminoimidazolidinium trifluoromethanesulfonate. Stang et al. synthesised a large number of dicationic ether salts of the formula R⁺—O—R⁺.2CF₃SO₃ ⁻. These salts are described as thermally stable, but very hygroscopic. The reaction of bis-(1,3-dimethylimidazolinium-2-yl) ether ditriflate with diethylamine gave 1,3-dimethyl-2-diethylaminoimidazolidinium trifluoromethanesulfonate as illustrative secondary reaction of the dicationic ether salts.

W. Kantlehner et al., Liebigs Ann. Chem. 1984, 108-126, report on the difficulty of synthesising tetraalkylguanidinium salts, with the focus on the synthesis of tetraalkylguanidinium halides, which are highly hygroscopic. In order to characterise these halides, hexamethylguanidinium or hexaethyl-guanidinium chlorides, in particular, were converted into corresponding salts, in particular salts having the anions perchlorate, methylsulfate, hexa-fluorophosphate, tetrafluoroborate and nitrate.

EP 1 363 345 explicitly discloses the compound tetramethylguanidinium bis(trifluoromethanesulfonyl)imide and the use thereof as electrolyte. EP 1 363 345 was published after filing of the priority-establishing application DE 10325051. Similar properties of this salt are assumed for compounds in which a proton or a plurality of protons of the guanidine unit are replaced by aliphatic substituents, such as ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl or halogenated alkyl groups, such as partially or fully halogenated ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tertbutyl, where halogen is intended to be F, Cl, Br, I or At, but the asymmetry of the guanidinium cation is said to be retained. The asymmetry of the guanidinium cation is understood in the sense that all three nitrogen atoms may not be identically substituted. However, alicyclic and aromatic groups may also be substituents of a proton or some protons of the guanidinium, in particular which form a mono-, bi- or tricyclic ring. An example thereof that is mentioned is 1-methyl-7-n-propyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium. Suitable anions, besides bis(trifluoromethanesulfonyl)imide, are also claimed to be hexafluorophosphate, tetrafluoroborate and trifluoromethane-sulfonate (triflate) or trifluoromethanesulfonyltrifluoroacetylimide, trifluoro-methanesulfonylpentafluoroethanesulfonylimide or closocarborates, such as B₉H₉CH⁻, B₁₁H₂₂CH⁻, closoborates, such as B₁₀H₁₀ ²⁻ and B₁₂H₁₂ ²⁻, and halogenated derivatives thereof, AsF₆ ⁻, SbF₆ ⁻, ClO₄ ⁻, O₂ ⁻, AlCl₄ ⁻, GaCl₄ ⁻, C(SO₂CF₃)₃ ⁻, SCN⁻, C₆F₅SO₃ ⁻, O₂CCF₃ ⁻, SO₆F⁻ and B(C₆H₅)₄ ⁻.

N. M. M. Mateus et al., Green Chem. 2003, 5, 347-352, disclose N,N-di-methyltetraalkylguanidinium salts and the preparation thereof, as revealed by the following reaction scheme:

Compounds 3: X⁻=PF₆ ⁻, compounds 4: X⁻=BF₄ ⁻,

compounds 5: X⁻=[(CF₃SO₃)₂N]⁻,

a: R¹=R²=n-butyl,

b: R¹=methyl, R²=n-butyl,

c: R¹=ethyl, R²=n-butyl,

d: R¹=R²=n-hexyl,

e: R¹=R²=n-octyl.

These N,N-dimethylguanidinium salts are furthermore described as a new generation of ionic liquids. A viscosity is only quoted for compound 5d, but is very high at 346 cP at 25° C.

The object of providing stable salt-like compounds of low viscosity which can be used as ionic liquids is achieved in accordance with the invention by salts having guanidinium cations in which the positive charge is delocalised over a plurality of nitrogen atoms, in accordance with the general formula (1)

The groups R here have the meaning of

-   -   H     -   straight-chain or branched alkyl having 1-20 C atoms, or in the         case of A⁻=[(C₂F₅)₃PF₃]⁻ straight-chain or branched alkyl having         2-20 C atoms or     -   saturated, partially or fully unsaturated cycloalkyl having 3-7         C atoms, which may be substituted by alkyl groups having 1-6 C         atoms, in particular phenyl,

where the R are in each case identical or different,

where up to four R may be connected to one another in pairs by a single or double bond,

where one or more R may be partially or fully substituted by halogens, in particular —F and/or —Cl, or partially by —CN or —NO₂,

and where one or two non-adjacent carbon atoms of the R may be replaced by atoms and/or atom groups selected from the group —O—, —C(O)—, —C(O)O—, —S—, —S(O)—, —SO₂—, —SO₂O—, —N═, —N═N—, —NH—, —NR′—, —PR′—, —P(O)R′—, —P(O)R′—O—, —O—P(O)R′—O—, —P(O)(NR′₂)—NR′— and —PR′₂═N—, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl or an unsubstituted or substituted heterocycle,

and A⁻ is selected from the group consisting of:

[(FSO₂)₂N]⁻, [R^(F)CF₂SO₃]⁻, [(R^(F′)SO₂)₂N]⁻, [(R^(F′)SO₂)₃C]⁻, [(FSO₂)₃C]⁻, [R^(F)CF₂C(O)O]⁻, [P(C_(n)F_(2n+1-m)H_(m))_(y)F_(6-y)]⁻, [P(C₆F₅)_(y)F_(6-y)]⁻, [R^(F) ₂P(O)O]⁻, [R^(F)P(O)O₂]²⁻, [BF_(z)R^(F) _(4-z)]⁻, [BF_(z)(CN)_(4-z)]⁻, [N(CF₃)₂]⁻, [N(CN)₂]⁻, [C(CN)₃]⁻ or

where

-   -   R^(F)=perfluorinated and straight-chain or branched alkyl having         1-20 C atoms, preferably having 1-12 C atoms,     -   perfluorinated and straight-chain or branched alkenyl having         2-20 C atoms and one or more double bonds,     -   perfluorinated and straight-chain or branched alkynyl having         2-20 C atoms and one or more triple bonds,     -   perfluorinated and saturated, partially or fully unsaturated         cycloalkyl having 3-7 C atoms, in particular phenyl, which may         be substituted by perfluoroalkyl groups,

where a plurality of R^(F) may in each case be identical or different,

where the R^(F) may be connected to one another in pairs by a single or double bond,

and where one or two non-adjacent carbon atoms of the R^(F) which are not in the a-position to the heteroatom may be replaced by atoms and/or atom groups selected from the group —O—, —SO₂— and —NR′— or by the end group —SO₂X′, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl, including —C₆F₅, or an unsubstituted or substituted heterocycle, and X′=F, Cl or Br,

and

-   -   R^(F′)=perfluorinated and straight-chain or branched alkyl         having 2-20 C atoms,     -   perfluorinated and straight-chain or branched alkenyl having         2-20 C atoms and one or more double bonds,     -   perfluorinated and straight-chain or branched alkynyl having         2-20 C atoms and one or more triple bonds,     -   perfluorinated and saturated, partially or fully unsaturated         cycloalkyl having 3-7 C atoms, in particular phenyl, which may         be substituted by perfluoroalkyl groups,

where a plurality of R^(F′) may in each case be identical or different,

where the R^(F′) may be connected to one another in pairs by a single or double bond,

and where one or two non-adjacent carbon atoms of the R^(F′) which are not in the α-position to the heteroatom may be replaced by atoms and/or atom groups selected from the group —O—, —SO₂— and —NR′— or by the end group —SO₂X′, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl, including —C₆F₅, or an unsubstituted or substituted heterocycle, and X′=F, Cl or Br,

n=1 to 20, preferably 1 to 12, and

m=0, 1, 2 or 3 and

y=1, 2, 3 or 4 and

z=0, 1, 2 or 3 and

—X— and —Y— are in each case identical or different and denote —C(O)—C(O)—, —C(O)—(CH₂)_(q)—C(O)—, where q=1, 2 or 3, —C(O)—(CF₂)_(q)—C(O)—, where q=1, 2 or 3, —C(CF₃)₂—C(CF₃)₂—,

where k=1, 2, 3 or 4 and p=1 or 2.

For the purposes of the present invention, fully unsaturated substituents are also taken to mean aromatic substituents.

The compounds according to the invention are distinguished, in particular, by very stable cations.

The compounds according to the invention are accordingly salts which have an optionally substituted guanidinium cation.

Besides hydrogen, suitable substituents R of the guanidinium cation are, in accordance with the invention: C₁- to C₂₀-, in particular C₁- to C₁₂-alkyl groups, and saturated or unsaturated, i.e. also aromatic, C₃- to C₇-cycloalkyl groups, which may be substituted by C₁- to C₆-alkyl groups, in particular phenyl. The six substituents R of the guanidinium cation according to the invention may be identical or different here.

The C₁-C₆-alkyl group is, for example, methyl, ethyl, isopropyl, propyl, butyl, sec-butyl or tert-butyl, furthermore also pentyl, 1-, 2- or 3-methylbutyl, 1,1-, 1,2- or 2,2-dimethylpropyl, 1-ethylpropyl or hexyl, if desired difluoromethyl, trifluoromethyl, pentafluoroethyl, heptafluoropropyl or nonafluorobutyl.

Unsubstituted saturated or partially or fully unsaturated cycloalkyl groups having 3-7 C atoms are therefore cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclopenta-1,3-dienyl, cyclohexenyl, cyclohexa-1,3-dienyl, cyclohexa-1,4-dienyl, phenyl, cycloheptenyl, cyclohepta-1,3-dienyl, cyclohepta-1,4-dienyl or cyclohepta-1,5-dienyl, which may be substituted by C₁- to C₆-alkyl groups, where the cycloalkyl group or the cycloalkyl group substituted by C₁- to C₆-alkyl groups may in turn also be substituted by halogen atoms, such as F, Cl, Br or I, in particular F or Cl, CN or NO₂.

The substituents R may be partially or fully substituted by halogen atoms, in particular by F and/or Cl, or partially by CN or NO₂. Furthermore, the substituents R may contain one or two mutually adjacent heteroatoms or atom groups selected from the group —O—, —C(O)—, —C(O)O—, —S—, —S(O)—, —SO₂—, —SO₂O—, —N═, —N═N—, —NH—, —NR′—, —PR′—, —P(O)R′—, —P(O)R′—O—, —O—P(O)R′—O—, —P(O)(NR′₂)—NR′— and —PR′₂═N—, where R′ can be an unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl or an unsubstituted or substituted heterocycle which are not in the α-position to a nitrogen atom of the guanidinium.

In R′, C₃- to C₇-cycloalkyl is, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl.

In R′, substituted phenyl denotes phenyl which is substituted by C₁- to C₆-alkyl, C₁- to C₆-alkenyl, NO₂, F, Cl, Br, I, OH, C₁-C₆-alkoxy, CN, SCN, SCF₃, SO₂CF₃, C(O)O—C₁-C₆-alkyl, NH₂, C₁-C₆-alkylamino or C₁-C₆-dialkylamino, COOH, C(O)NR″₂, SO₂OR″, SO₂X′, SO₂NR″₂, SO₃H or NHC(O)R″, where X′ denotes F, Cl or Br, and R″ denotes an unfluorinated, partially or perfluorinated C₁- to C₆-alkyl or C₃- to C₇-cycloalkyl as defined for R′, for example o-, m- or p-methylphenyl, o-, m- or p-ethylphenyl, o-, m- or p-propylphenyl, o-, m- or p-isopropylphenyl, o-, m- or p-tert-butylphenyl, o-, m- or p-aminophenyl, o-, m- or p-(N,N-dimethylamino)phenyl, o-, m- or p-nitrophenyl, o-, m- or p-hydroxyphenyl, o-, m- or p-methoxyphenyl, o-, m- or p-ethoxyphenyl, o-, m- or p-(trifluoromethyl)phenyl, o-, m- or p-(trifluoromethoxy)phenyl, o-, m- or p-(trifluoromethylsulfonyl)phenyl, o-, m- or p-fluorophenyl, o-, m- or p-chlorophenyl, o-, m- or p-bromophenyl, o-, m- or p-iodophenyl, furthermore preferably 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-di-methylphenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dihydroxyphenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-difluorophenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-di-chlorophenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dibromophenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dimethoxyphenyl, 5-fluoro-2-methylphenyl, 3,4,5-tri-methoxyphenyl or 2,4,5-trimethylphenyl.

In R′, heterocycle is taken to mean a saturated or unsaturated mono- or bi-cyclic heterocyclic radical having 5 to 13 ring members, where 1, 2 or 3 N and/or 1 or 2 S or O atoms may be present, and the heterocyclic radical may be mono- or polysubstituted by C₁- to C₆-alkyl, C₁- to C₆-alkenyl, NO₂, F, Cl, Br, I, OH, C₁-C₆-alkoxy, CN, SCN, SCF₃, SO₂CF₃, C(O)O—C₁-C₆-alkyl, NH₂, C₁-C₆-alkylamino or C₁-C₆-dialkylamino, COOH, C(O)NR″₂, SO₂OR″, SO₂X′, SO₂NR″₂, SO₃H or NHC(O)R″, where X′ and R″ have a meaning indicated above.

The heterocyclic radical is preferably substituted or unsubstituted 2- or 3-furyl, 2- or 3-thienyl, 1-, 2- or 3-pyrrolyl, 1-, 2-, 4- or 5-imidazolyl, 3-, 4- or 5-pyrazolyl, 2-, 4- or 5-oxazolyl, 3-, 4- or 5-isoxazolyl, 2-, 4- or 5-thiazolyl, 3-, 4- or 5-isothiazolyl, 2-, 3- or 4-pyridyl, 2-, 4-, 5- or 6-pyrimidinyl, furthermore preferably 1,2,3-triazol-1-, -4- or -5-yl, 1,2,4-triazol-1-, 4- or -5-yl, 1- or 5-tetrazolyl, 1,2,3-oxadiazol-4- or -5-yl, 1,2,4-oxadiazol-3- or -5-yl, 1,3,4-thiadiazol-2- or -5-yl, 1,2,4-thiadiazol-3- or -5-yl, 1,2,3-thiadiazol4- or -5-yl, 2-, 3-, 4-, 5- or 6-2H-thiopyranyl, 2-, 3- or 4-4H-thiopyranyl, 3- or 4-pyridazinyl, pyrazinyl, 2-, 3-, 4-, 5-, 6- or 7-benzofuryl, 2-, 3-, 4-, 5-, 6- or 7-benzothienyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-1 H-indolyl, 1-, 2-, 4- or 5-benzimidazolyl, 1-, 3-, 4-, 5-, 6- or 7-benzopyrazolyl, 2-, 4-, 5-, 6- or 7-benzoxazolyl, 3-, 4-, 5-, 6- or 7-benzisoxazolyl, 2-, 4-, 5-, 6- or 7-benzothiazolyl, 2-, 4-, 5-, 6- or 7-benzisothiazolyl, 4-, 5-, 6- or 7-benz-2,1,3-oxadiazolyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-quinolinyl, 1-, 3-, 4-, 5-, 6-, 7- or 8-isoquinolinyl, 1-, 2-, 3-, 4-, or 9-carbazolyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-acridinyl, 3-, 4-, 5-, 6-, 7-, or 8-cinnolinyl, 2-, 4-, 5-, 6-, 7- or 8-quinazolinyl or 1-, 2- or 3-pyrrolidinyl.

Without restricting generality, examples of substituents R of the guanidinium cation are:

—CH₃, —C₂H₅, —C₃H₇, —CH(CH₃)₂, —C₄H₉, —C(CH₃)₃, —C₅H₁₁, —C₆H₁₃, —C₇H₁₅, —C₈H₁₇, —C₉H₁₉, —C₁₀H₂₁, —C₁₂H₂₅, —C₂₀H₄₁, —OCH₃, —OCH(CH₃)₂, —CH₂OCH₃, —C₂H₄OCH(CH₃)₂, —C₂H₄SC₂H₅, —C₂H₄SCH(CH₃)₂, —S(O)CH₃, —SO₂CH₃, —SO₂C₆H₅, —SO₂C₃H₇, —SO₂CH(CH₃)₂, —SO₂CH₂CF₃, —CH₂SO₂CH₃, —CH₂N(H)C₂H₅, —C₂H₄N(H)C₂H₅, —CH₂N(CH₃)CH₃, —CN, —C₂H₄N(CH₃)CH₃, —NH₂, —NHC₂H₅, —N(CH₃)₂, —N(CH₃)C₂H₅, —N(CH₃)CF₃, —O—C₄H₈—O—C₄H₉, —CF₃, —C₂F₅, —C₃F₇, —C₄F₉, —C(CF₃)₃, —CF₂SO₂CF₃, —C₂F₄N(C₂F₅)C₂F₅, —CHF₂, —CH₂CF₃, —C₂F₂H₃, —C₃FH₆, —CH₂C₃F₇, —C(CFH₂)₃, —CH₂C(O)OH, —CH₂C₆H₅, —CH₂C(O)CH₃, —CH₂C(O)C₂H₅, —CH₂C(O)OCH₃, CH₂C(O)OC₂H₅, —C(O)CH₃, —C(O)C₆H₅, —C(O)OCH₃, —C(O)OC₂H₅, P(O)(C₂H₅)₂, P(O)[N(C₂H₅)₂]₂,

Up to four substituents R may also be connected in pairs in such a way that mono-, bi- or polycyclic cations are formed.

Without restricting generality, examples of such guanidinium cations are:

where the substituents R can have an above-mentioned or particularly preferred meaning.

If desired, the carbocyclic or heterocyclic rings of the above-mentioned guanidinium cations may also be substituted by C₁- to C₆-alkyl, C₁- to C₆-alkenyl, NO₂, F, Cl, Br, I, OH, C₁-C₆-alkoxy, CN, SCN, SCF₃, SO₂CF₃, C(O)O—C₁-C₆-alkyl, NH₂, C₁-C₆-alkylamino or C₁-C₆-dialkylamino, COOH, C(O)NR″₂, SO₂OR″, SO₂NR″₂, SO₂X′, SO₃H or NHC(O)R″, where X′ and R″ have a meaning indicated above, substituted or unsubstituted phenyl or an unsubstituted or substituted heterocycle.

The anion A⁻ of the salts according to the invention is selected from [(FSO₂)₂N]⁻, [R^(F)CF₂SO₃]⁻, [(R^(F′)SO₂)₂N]⁻, [(R^(F′)SO₂)₃C]⁻, [(FSO₂)₃C]⁻, [R^(F)CF₂C(O)O]⁻, [P(C_(n)F_(2n+1-m)H_(m))_(y)F_(6-y)]⁻, [P(C₆F₅)_(y)F_(6-y)]⁻, [R^(F) ₂P(O)O]⁻, [R^(F)P(O)O₂]²⁻, [BF_(z)R^(F) _(4-z)]⁻, [BF_(z)(CN)_(4-z)]⁻, [N(CF₃)₂]⁻, [N(CN)₂]⁻, [C(CN)₃]⁻ or

In accordance with the invention, suitable organic groups R^(F) or R^(F′) of the anion are: C₁- or C₂- to C₂₀-, in particular C₁- or C₂- to C₁₂-alkyl groups respectively, C₂- to C₂₀-, in particular C₂- to C₁₂-alkenyl- or -alkynyl groups and saturated or unsaturated, i.e. also aromatic, C₃- to C₇-cycloalkyl groups, which may be substituted by C₁- to C₆-alkyl groups, in particular phenyl, where all the groups listed are in perfluorinated form.

A straight-chain or branched alkenyl having 2 to 20 C atoms, where a plurality of double bonds may also be present, is, for example, allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore 4-pentenyl, isopentenyl, hexenyl, heptenyl, octenyl, —C₉H₁₇, —C₁₀H₁₉ to —C₂₀H₃₉, preferably allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore preferably 4-pentenyl, isopentenyl or hexenyl.

A straight-chain or branched alkynyl having 2 to 20 C atoms, where a plurality of triple bonds may also be present, is, for example, ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, furthermore 4-pentynyl, 3-pentynyl, hexynyl, heptynyl, octynyl, —C₉H₁₅, —C₁₀H₁₇ to —C₂₀H₃₇, preferably ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, 4-pentynyl, 3-pentynyl or hexynyl.

In the case where a plurality of R^(F) or R^(F′) are present in one anion, these may also be connected in pairs by single or double bonds in such a way that bi- or polycyclic anions are formed.

Furthermore, the substituents R^(F) or R^(F′) may contain one or two atoms or atom groups which are not adjacent to one another and are not in the α-position to the heteroatom, selected from the group —O—, —SO₂— and —NR′—, or the end group —SO₂X′, where R′ can be unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl, including —C₆F₅, or an unsubstituted or substituted heterocycle, and X′=F, Cl or Br.

Without restricting generality, examples of substituents R^(F) and R^(F′) of the anion are:

—CF₃, —C₂F₅, —C₃F₇, —C₄F₉, —C(CF₃)₃, —CF₂N(CF₃)CF₃, —CF₂OCF₃, —CF₂S(O)CF₃, —CF₂SO₂CF₃, —C₂F₄N(C₂F₅)C₂F₅, CF═CF₂, —C(CF₃)═CFCF₃, —CF₂CF═CFCF₃, —CF═CFN(CF₃)CF₃ or —CF₂SO₂F, —C(CF₃)═CFCF₃, —CF₂CF═CFCF₃ or —CF═CFN(CF₃)CF₃.

R^(F′) is preferably pentafluoroethyl, heptafluoropropyl or nonafluorobutyl. R^(F) is preferably trifluoromethyl, pentafluoroethyl, heptafluoropropyl or nonafluorobutyl.

Without restricting generality, some examples of anions according to the invention are shown below: [(FSO₂)₂N]⁻, [CF₃CF₂SO₃]⁻, [(C₂F₅SO₂)₂N]⁻, [(C₂F₅SO₂)₃C⁻, [(FSO₂)₃C]⁻, [CF₃CF₂C(O)O]⁻, [P(C₂F₅)₃F₃]⁻, [P(CF₃)₃F₃]⁻, [P(C₂F₄H)(CF₃)₂F₃]⁻, [P(C₂F₃H₂)₃F₃]⁻, [P(C₂F₅)(CF₃)₂F₃]⁻, [P(C₆F₅)₃F₃]⁻, [P(C₃F₇)₃F₃]⁻, [P(C₄F₉)₃F₃]⁻, [P(C₂F₅)₂F₄]⁻, [(C₂F₅)₂P(O)O]⁻, [(C₂F₅)P(O)O₂]²⁻, [P(C₆F₅)₂F₄]⁻, [(CF₃)₂P(O)O]⁻, [(C₄F₉)₂P(O)O]⁻, [CF₃P(O)O₂]⁻, [BF₃(CF₃)]⁻, [BF₂(C₂F₅)₂]⁻, [BF₃(C₂F₅)]⁻, [BF₂(CF₃)₂]⁻, [B(C₂F₅)₄]⁻, [BF₃(CN)]⁻, [BF₂(CN)₂]⁻, [B(CN)₄]⁻, [B(CF₃)₄]⁻, [N(CF₃)₂]⁻, [N(CN₂)₂]⁻, [C(CN)₃]⁻,

Very preferred anions of this group are [P(C_(n)F_(2n+1-m)H_(m))_(y)F_(6-y)]⁻, [BF_(z)R^(F) _(4-z)]⁻ and [BF_(z)(CN)_(4-z)]⁻, where n, m, y and z have one of the above-mentioned meanings, for example [B(CN)₄]⁻, [(C₂F₅)₃PF_(3]) ⁻, [(C₂F₅)₂PF₄]⁻, [(C₄F₉)₃PF₃]⁻, [(C₃F₇)₃PF₃]⁻, [B(C₂F₅)F₃]⁻ or [B(CF₃)₄]⁻. Very particulary preferred anions of this group are [B(CN)₄]⁻, [(C₂F₅)₃PF₃]⁻ or [B(C₂F₅)F₃]⁻.

In accordance with the invention, preference is given to a group of salts of the formula (1) in which the substituents R of the guanidinium cation denote hydrogen or a straight-chain or branched alkyl group having 1-12 C atoms, in particular having 1-4 C atoms, and A⁻ has a meaning indicated for the formula (1) or a preferred or particularly preferred meaning.

In accordance with the invention, preference is given to a group of salts of the formula (1) in which the substituents R of the guanidinium cation are selected from the group methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, phenyl and cyclohexyl, and A⁻ has a meaning indicated for the formula (1) or a preferred or particularly preferred meaning.

In accordance with the invention, preference is given to a group of salts of the formula (1) in which at least two substituents R are connected to one another by single or double bonds in such a way that a monocyclic cation is formed, and A⁻ has a meaning indicated for the formula (1) or a preferred or particularly preferred meaning.

In accordance with the invention, particular preference is given to a group of salts in which the substituents R each, independently of one another, denote hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl or i-butyl or two substituents R are connected to one another in such a way that an imidazolidinium cation is formed, and A⁻ has a meaning indicated for the formula (1) or a preferred or particularly preferred meaning.

The present invention secondly relates to a process for the preparation of the salts having guanidinium cations of the general formula (1) according to the invention. To this end, a guanidine (NR₂)₂C═(NR) or a guanidinium salt C(NR₂)₃ ⁺ X⁻ is reacted with an acid AH, a salt Kt⁺ A⁻ or an ester AR.

The anion X⁻ of the reacting guanidinium salt is selected here from the group F⁻, Cl⁻, Br⁻, I⁻, [HF₂]⁻, [CN]⁻, [SCN]⁻, [CH₃COO]⁻, [CF₃COO]⁻, [CF₃SO₃]⁻, [CH₃OSO₃]⁻, [SiF₆]²⁻, [BF₄]⁻, [SO₄]²⁻, [NO₃]⁻, [C₂H₅OSO₃]⁻, tosylates, malonates, substituted malonates and [CO₃]⁻. X⁻ is preferably F⁻, Cl⁻, Br⁻, I⁻, [HF₂]⁻, [CH₃OSO₃]⁻, [CF₃COO]⁻, [CF₃SO₃]⁻ or [CO₃]⁻, particularly preferably Cl⁻, Br⁻, [CH₃OSO₃]⁻ or [CF₃SO₃]⁻.

The groups and substituents A and R here are defined like those of the general formula (1), and Kt is an alkali or alkaline earth metal, where, for the ester AR, perhalogenated alkyl groups having 1-20 C atoms, cycloalkyl groups having 3-7 C atoms, alkenyl groups having 2-20 C atoms and alkynyl groups having 2-20 C atoms are excluded for the meaning of the substituents R.

The reaction is preferably carried out at a temperature at which at least one of the components is liquid. The reaction is particularly preferably carried out in a temperature range in which the reaction mixture is liquid.

The reaction of the guanidine or guanidinium salt with an acid AH or a salt Kt⁺ A⁻ can be carried out in polar inorganic or organic solvents, for example water, acetonitrile, dimethoxyethane, methanol, dimethylformamide, propionitrile or dichloromethane. The reaction with an ester, an acid or a salt can be carried out in nonpolar organic solvents as diluent, for example hexane or pentane, or without solvents, for example in the salt melt. The alkylation of the guanidine using an ester can be carried out in a non-basic solvent, preferably hexane, pentane or dichloromethane. In accordance with the invention, solvent mixtures can also be used instead of pure solvents.

In accordance with the invention, the reagents in the alkylation can be reacted with an up to five-fold excess of one of the reactants, in particular of the alkylating agent. However, the reactants are preferably employed in equimolar amount.

The salts according to the invention can be isolated with very good yields, generally greater than 80%, preferably greater than 90%.

The present invention furthermore relates to a process for the preparation of a salt having a guanidinium cation of the general formula (1) and a [BF₄]⁻ anion, where R has a meaning indicated for the formula (1) or a preferred meaning, which process can furthermore be used for the preparation of the guanidinium salts according to the invention. In this process, firstly a guanidinium chloride C(NR₂)₃ ⁺ Cl⁻ or a guanidinium bromide C(NR₂)₃ ⁺ Br⁻, where the radicals R are defined in accordance with the general formula (1), is reacted with anhydrous HF, and the guanidinium fluoride formed in situ is subsequently reacted with boron trifluoride etherate BF₃*Et₂O.

Guanidinium tetrafluoroborates are advantageously formed in this process according to the invention with a reduced amount of chloride ions, i.e. the proportion of chloride ions is <100 ppm, preferably <50 ppm.

The anhydrous hydrofluoric acid functions both as solvent and also as reagent in this reaction.

The reaction is preferably carried out at a temperature at which at least one of the components is liquid. The reaction is particularly preferably carried out in a temperature range in which the reaction mixture is liquid.

In accordance with the invention, the boron trifluoride etherate can be employed in an excess of up to 10% in relation to the guanidinium salt. However, the reactants are preferably employed in equimolar amount.

All compounds according to the invention have a salt-like character, relatively low melting points (usually below 100° C.) and can be used as ionic liquids. In particular, they have, as described above, particularly low viscosities.

The salts according to the invention can be employed as solvents for many synthetic or catalytic reactions, for example Friedel-Crafts acylation and alkylation, Diels-Alder cycloadditions, hydrogenation and oxidation reactions or Heck reactions.

The use of the compounds according to the invention as non-aqueous electrolyte, optionally in combination with other electrolytes known to the person skilled in the art, is also possible.

In addition, the salts according to the invention can be used as non-aqueous polar substances in suitable reactions as phase-transfer catalyst, as surfactant (surface-active agent) or as medium for the heterogenisation of homogeneous catalysts.

They are furthermore suitable as desiccants and as separating agents for gases. This use is particularly preferred for the triflates according to the invention.

The complete disclosure content of all applications, patents and publications mentioned above and below is incorporated into this application by way of reference.

Even without further comments, it is assumed that a person skilled in the art will be able to utilise the above description in the broadest scope. The preferred embodiments and examples should therefore merely be regarded as descriptive disclosure which is absolutely not limiting in any way.

The NMR spectra were measured on solutions in deuterated solvents at 20° C. in a Bruker Avance 300 spectrometer with a 5 mm ¹H/BB broad-band head with deuterium lock, unless indicated otherwise in the examples. Measurement frequencies of the various nuclei are: ¹H: 300.13 MHz, ¹¹B: 96.92 MHz, ¹⁹F: 282.41 MHz and ³¹P: 121.49 MHz. The referencing method is indicated separately for each spectrum or for each data set.

EXAMPLE 1 Hexamethylguanidinium triflate

9.50 g (52.9 mmol) of hexamethylguanidinium chloride are dissolved in 100 cm³ of water. 8.03 g (53.5 mmol) of trifluoromethanesulfonic acid are added at room temperature while the reaction mixture is stirred using a magnetic stirrer. The water is removed in a rotary evaporator together with volatile by-products. The residue is washed twice with 50 cm³ of diethyl ether and dried at 50-60° C. under a vacuum of 7.0 Pa, giving 14.8 g of a solid material (m.p.=174-176° C.). The yield of hexamethylguanidinium triflate is 95.4%, based on hexamethylguanidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −77.89 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 2.89 s (CH₃).

EXAMPLE 2 Hexamethylguanidinium tris(pentafluoroethyl)trifluorophosphate

5.00 g (27.8 mmol) of hexamethylguanidinium chloride are dissolved in 150 cm³ of water. 15.38 g (28.7 mmol) of tris(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred using a magnetic stirrer. The precipitate is filtered off, washed four times with 50 cm³ of water and dried at 50-60° C. under a vacuum of 7.0 Pa, giving 16.2 g of a solid material (m.p.=128-129° C.). The yield of hexamethylguanidinium tris(pentafluoroethyl)trifluorophosphate is 98.9%, based on hexamethylguanidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.50 dm (PF); −79.52 m (CF₃); −81.21 m (2CF₃); −86.87 dm (PF₂); −114.91 m (CF₂); −115.49 m (2CF₂); ¹J_(P,F)=889 Hz; ¹J_(P,F)=901 Hz; ²J_(P,F)=85 Hz; ²J_(P,F)=98 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 2.89 s (CH₃).

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.59 dtm;

¹J_(P,F)=890 Hz; ¹J_(P,F)=902 Hz.

Elemental Analysis

Found, %: C 26.57 H 3.05 N 7.15

Calculated for C₁₃H₁₈F₁₈N₃P, %: C 26.50 H 3.08 N 7.13

EXAMPLE 3 N,N,N′,N′,N″-pentamethyl—N″-n-propylguanidinium triflate

10.47 g (66.6 mmol) of N,N,N′,N′-tetramethyl-N″-n-propylguanidine are dissolved in 80 cm³ of pentane. 10.94 g (66.7 mmol) of methyl triflate, CF₃SO₂OCH₃, are slowly added (dropwise) at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The precipitate is filtered off and washed with 40 cm³ of pentane and dried at 50-60° C. under a vacuum of 7.0 Pa, giving 21.4 g of a solid material (m.p.=109-110° C.). The yield of N,N,N′,N′,N″-pentamethyl-N″-n-propylguanidinium triflate is approximately quantitative.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −77.89 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 0.91 t (CH₃); 1.56 br.s (1H, CH₂); 1.70 br.s (1H, CH₂); 3.13 m (CH₂); 2.88 s (CH₃); 2.90 s (4CH₃); ³J_(H,H)=7.3 Hz.

EXAMPLE 4 N,N,N′,N′,N″-pentamethyl-N″-i-propylguanidinium triflate

8.27 g (52.6 mmol) of N,N,N′,N′-tetramethyl-N″-i-propylguanidine are dissolved in 80 cm³ of pentane. 8.64 g (52.7 mmol) of methyl triflate, CF₃SO₂OCH₃, are slowly added (dropwise) at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The precipitate is filtered off and washed with 40 cm³ of pentane and dried at 50-60° C. under a vacuum of 7.0 Pa, giving 16.9 g of a solid material (m.p.=103-105° C.). The yield of N,N,N′,N′,N″-pentamethyl-N″-i-propylguanidinium triflate is approximately quantitative.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −77.91 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 1.20 br.s (CH₃); 1.32 br.s (CH₃); 2.77 s (CH₃); 2.91 s (4CH₃); 3.74 hep. (CH); 3J_(H,H)=6.6 Hz.

EXAMPLE 5 N,N,N′,N′,N″-pentamethyl-N″-n-propylguanidinium tris(pentafluoroethyl)trifluorophosphate

8.00 g (24.9 mmol) of N,N,N′,N′,N″-pentamethyl-N″-n-propylguanidinium triflate are dissolved in 100 cm³ of water, and 13.40 g (25.0 mmol) of tris-(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is cooled using an ice bath, and the aqueous solution (upper phase) is decanted off. The viscous liquid (lower phase) is washed three times with 30 cm³ of ice-water. The residue is dried at 50-60° C. unde a vacuum of 7.0 Pa, giving 14.2 g of a liquid. The yield of N,N,N′, N′, N″-pentamethyl-N″-n-propylguanidinium tris(pentafluoroethyl)trifluorophosphate is 92.4%, based on N,N,N′,N′,N″-pentamethyl-N″-n-propylguanidinium triflate.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.54 dm (PF); −79.54 m (CF₃); −81.22 m (2CF₃); −86.91 dm (PF₂); −114.88 m (CF₂); −115.49 m (2CF₂); ¹J_(P,F)=890 Hz; ¹J_(P,F)=901 Hz; ²J_(P,F)=84 Hz; ²J_(P,F)=98 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 0.92 t (CH₃); 1.56 br.s (1H, CH₂); 1.72 br.s (1H, CH₂); 3.13 m (CH₂); 2.88 s (CH₃); 2.90 s (4CH₃); ³J_(H,H)=7.3 Hz.

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.53 dtm; ¹J_(P,F)=890 Hz; ¹J_(P,F)=902 Hz.

EXAMPLE 6 N,N,N′,N′,N″-pentamethyl-N″-i-propylguanidinium tris(pentafluoroethyl)trifluorophosphate

6.80 g (21.2 mmol) of N,N,N′,N′,N″-pentamethyl-N″-i-propylguanidinium triflate are dissolved in 100 cm³ of water. 11.40 g (21.3 mmol) of tris(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The residue is filtered off, washed three times with 30 cm³ of ice-water and dried at 50-60° C. under a vacuum of 7.0 Pa, giving 12.3 g of a solid material (m.p.=68-69° C.). The yield of N,N,N′,N′, N″-pentamethyl-N″-i-propylguanidinium tris(pentafluoroethyl)trifluorophosphate is 94.0%, based on N,N,N′,N′,N″-pentamethyl-N″-i-propylguanidinium triflate.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.52 dm (PF); −79.55 m (CF₃); −81.21 m (2CF₃); −86.84 dm (PF₂); −114.89 m (CF₂); −115.50 m (2CF₂); ¹J_(P,F)=889 Hz; ¹J_(P,F)=901 Hz; ²J_(P,F)=87 Hz; ²J_(P,F)=97 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 1.22 br.s (CH₃); 1.33 br.s (CH₃); 2.77 s (CH₃); 2.91 s (4CH₃); 3.74 hep. (CH); ³J_(H,H)=6.6 Hz.

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.56 dtm; ¹J_(P,F)=890 Hz; ¹J_(P,F)=902 Hz.

EXAMPLE 7 Guanidinium triflate

6.5 g (36.1 mmol) of guanidinium carbonate are dissolved in 100 cm³ of water. 10.9 g (72.6 mmol) of trifluoromethanesulfonic acid are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The flask containing the reaction mixture is cooled using ice, and the precipitate is filtered off and washed twice with 30 cm³ of ice-water. The residue is dried at 50-60° C. under a vacuum of 7.0 Pa, giving 14.1 g of a solid material (m.p.=152-153° C.). The yield of guanidinium triflate is 93.4%, based on guanidinium carbonate.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −78.24 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 6.20 br.s (NH).

EXAMPLE 8 Guanidinium tris(pentafluoroethyl)trifluorophosphate

10.67 g (59.2 mmol) of guanidinium carbonate are dissolved in 250 cm³ of water. 63.5 g (118.4 mmol) of tris(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The flask containing the reaction mixture is cooled using ice, and the lower phase is separated off and washed twice with 30 cm³ of ice-water. The residue is dried at 50-60° C. under a vacuum of 7.0 Pa, giving 53.2 g of a solid material (m.p.=121-123° C.). The yield of guanidinium tris(pentafluoroethyl)trifluorophosphate is 89.0%.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.48 dm (PF); −79.54 m (CF₃); −81.23 m (2CF₃); −86.87 dm (PF₂); −114.89 m (CF₂); −115.47 m (2CF₂); ¹J_(P,F)=888 Hz; ¹J_(P,F)=901 Hz; ²J_(P,F)=84 Hz; ²J_(P,F)=98 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 5.94 br.s (NH).

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.53 dtm; ¹J_(P,F)=888 Hz; ¹J_(P,F)=902 Hz.

EXAMPLE 9 N,N,N′,N′-tetramethyl-N″-ethylguanidinium triflate

30.0 g (260.5 mmol) of N,N,N′,N′-tetramethylguanidine are dissolved in 150 cm³ of pentane, and 47.3 g (265.5 mmol) of ethyl triflate, CF₃SO₂OC₂H₅, are slowly added (dropwise) over the course of 30 min with ice-bath cooling and while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is stirred at room temperature for a further 10 min. The liquid lower phase is separated off and washed twice with 50 cm³ of pentane. The residue is dried at 40-50° C. for one hour under a vacuum of 7.0 Pa, giving 75.0 g of a liquid material. The yield of N,N,N′,N′-tetramethyl-N″-ethylguanidinium triflate is 98.2%.

The material is characterised by ¹⁹F and ¹H NMR spectroscopy, which show the formation of two isomers of N,N,N′,N′-tetramethyl-N″-ethylguanidinium triflate.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −77.95 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 1.15 t (CH₃); 1.22 t (CH₃); 2.89 br.s (CH₃); 2.91 br.s (CH₃); 2.92 s (2CH₃); 2.93 br.s (4CH₃); 3.22 q (CH₂); 5.47 s (NH); 6.04 br.s (NH); ³J_(H,H)=7.2 Hz.

Elemental Analysis

Found, %: C 32.82 H 6.26 N 14.25

Calculated for C₈H₁₈F₃N₃O₃S, %: C 32.76 H 6.19 N 14.33

EXAMPLE 10 N,N,N′, N′-tetramethyl-N″-ethylguanidinium tris(pentafluoroethyl)trifluorophosphate

29.7 g (101.3 mmol) of N,N,N′,N′-tetramethyl-N″-ethylguanidinium triflate are dissolved in 100 cm³ of water, and 57.0 g (106.3 mmol) of tris(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The lower liquid phase is separated off and washed four times with 50 cm³ of water. The residue is dried at 70° C. in an oil bath for three hours under a vacuum of 7.0 Pa, giving 56.1 g of a liquid material. The yield of N,N,N′,N′-tetramethyl-N″-ethylguanidinium tris(pentafluoroethyl)trifluorophosphate is 94.0%, based on N,N,N′,N′-tetramethyl-N″-ethylguanidinium triflate.

The material is characterised by ¹⁹F, ¹H and ³¹P NMR spectroscopy, which shows the formation of two isomers of N,N,N′,N′-tetramethyl-N″-ethylguanidinium tris(pentafluoroethyl)trifluorophosphate.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.55 dm (PF); −79.58 m (CF₃); −81.27 m (2CF₃); −86.93 dm (PF₂); −114.93 m (CF₂); −115.51 m (2CF₂); ¹J_(P,F)=889 Hz; ¹J_(P,F)=901 Hz; ²J_(P,F)=85 Hz; ²J_(P,F)=97 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 1.16 t (CH₃); 1.23 t (CH₃); 2.89 br.s (CH₃); 2.91 br.s (CH₃); 2.93 br.s (4CH₃); 2.94 s (2CH₃); 3.22 q (CH₂); 3.24 q (CH₂); 5.80 br. s (NH); 6.14 br.s (NH); ³J_(H,H)=7.2 Hz.

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.58 dtm; ¹J_(P,F)=888 Hz; ¹J_(P,F)=902 Hz.

EXAMPLE 11 1,3-Dimethyl-2-diethylaminoimidazolidinium chloride

30.0 g (177.5 mmol) of 1,3-dimethyl-2-chloroimidazolidinium chloride are dissolved in 70 cm³ of dry chloroform, and 27.1 g (186.5 mmol) of trimethylsilyldiethylamine (CH₃)₃SiN(C₂H₅)₂ are added slowly (dropwise) over the course of 30 min with ice-bath cooling and while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is subsequently stirred overnight at room temperature. The solvent is removed under reduced pressure. The residue is washed twice with 30 cm³ of hexane and dried at 60° C. for one hour under a vacuum of 7.0 Pa, giving 35.7 g of a crystalline material. The yield of 1,3-dimethyl-2-diethylaminoimidazolidinium chloride is 97.8%, based on 1,3-dimethyl-2-chloroimidazolidinium chloride.

¹H NMR (reference: TMS; solvent: CD₃CN): 1.16 t (2CH₃); 2.94 s (2CH₃); 3.33 q (2CH₂); 3.71 s (2CH₂); ³J_(H,H)=7.1 Hz.

EXAMPLE 12 1,3-Dimethyl-2-diethylaminoimidazolidinium tris(pentafluoroethyl)trifluorophosphate

15.0 g (72.9 mmol) of 1,3-dimethyl-2-diethylaminoimidazolidinium chloride are dissolved in 200 cm³ of water, and 41.0 g (76.5 mmol) of tris(pentafluoroethyl)trifluorophosphoric acid pentahydrate are added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The precipitate is filtered off and washed three times with 50 cm³ of water. The residue is dried at 50-60° C. in an oil bath for three hours under a vacuum of 7.0 Pa, giving 43.9 g of a solid white material (m.p. 36-37° C.). The yield of 1,3-dimethyl-2-diethylaminoimidazolidinium tris(pentafluoroethyl)trifluorophosphate is 97.8%, based on 1,3-dimethyl-2-diethylaminoimidazolidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −43.54 dm (PF); −79.57 m (CF₃); −81.26 m (2CF₃); −86.90 dm (PF₂); −114.92 m (CF₂); −115.51 m (2CF₂); ¹J_(P,F)=888 Hz; ¹J_(P,F)=900 Hz; ²J_(P,F)=85 Hz; ²J_(P,F)=98 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 1.20 t (2CH₃); 2.94 s (2CH₃); 3.34 q (2CH₂); 3.68 s (2CH₂); ³J_(H,H)=7.1 Hz.

³¹P NMR (reference: 85% H₃PO₄; solvent: CD₃CN): −148.57 dtm; ¹J_(P,F)=890 Hz; ¹J_(P,F)=902 Hz.

Elemental Analysis

Found, %: C 29.18 H 2.94 N 7.02

Calculated for C₁₅H₂₀F₁₈N₃P, %: C 29.28 H 3.28 N 6.83

EXAMPLE 13 1,3-Dimethyl-2-diethylaminoimidazolidinium triflate

10.98 g (53.4 mmol) of 1,3-dimethyl-2-diethylaminoimidazolidinium chloride are dissolved in 70 cm³ of water, and 8.24 g (54.9 mmol) of trifluoromethanesulfonic acid are added at room temperature over the course of 5 min while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is stirred at room temperature for a further 5 min. All volatile components of the mixture are removed under reduced pressure. The residue is washed twice with 50 cm³ of diethyl ether and dried at 60° C. in an oil bath for three hours under a vacuum of 7.0 Pa, giving 16.7 g of a crystalline material (m.p. 67-68° C.). The yield of 1,3-dimethyl-2-diethyl-aminoimidazolidinium triflate is 97.9%, based on 1,3-dimethyl-2-diethyl-aminoimidazolidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −77.92 s (CF₃).

¹H NMR (reference: TMS; solvent: CD₃CN): 1.18 t (2CH₃); 2.94 s (2CH₃); 3.34 q (2CH₂); 3.69 s (2CH₂); ³J_(H,H)=7.1 Hz.

EXAMPLE 14 Hexamethylguanidinium tetracyanoborate

4.54 g (29.5 mmol) of potassium tetracyanoborate are dissolved in 100 cm³ of water, and a solution of 5.30 g (29.5 mmol) of hexamethylguanidinium chloride in 15 cm³ of water is added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is stirred at room temperature for a further 20 min. The precipitate is filtered off and washed twice with 10 cm³ of water. The residue is dried at 60° C. in an oil bath for three hours under a vacuum of 7.0 Pa, giving 5.50 g of a solid white material (m.p. 123-124° C.). The yield of hexamethylguanidinium tetracyanoborate is 72.0%, based on hexamethyl-guanidinium chloride.

¹H NMR (reference: TMS; solvent: CD₃CN): 2.90 s (CH₃).

¹¹B NMR (reference: BF₃ ? O(C₂H₅)₂; solvent: CD₃CN): −38.23 s.

EXAMPLE 15 Hexamethylguanidinium pentafluoroethyltrifluoroborate

0.40 g (2.23 mmol) of hexamethylguanidinium chloride is dissolved in 2 cm³ of water, and a solution of 0.51 g (2.26 mmol) of potassium pentafluoroethyltrifluoroborate in 3 cm³ of water is added at room temperature while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is stirred at room temperature for a further 20 min. The precipitate is filtered off and washed twice with 3 cm³ of water. The residue is dried for three hours at 55-60° C. in an oil bath under a vacuum of 7.0 Pa, giving 0.69 g of a solid white material (m.p. 78-79° C.). The yield of hexamethylguanidinium pentafluoroethyltrifluoroborate is 93.5%, based on hexamethylguanidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −83.08 q (CF₃); −135.79 q (CF₂) −152.82 q,q (BF₃); ⁴J_(F,F)=4.8 Hz; ²J_(B,F)=19.3 Hz; ¹J_(B,F)=40.7 Hz.

¹H NMR (reference: TMS; solvent: CD₃CN): 2.89 s (6CH₃).

¹¹B NMR (reference: BF₃ ? O(C₂H₅)₂; solvent: CD₃CN): −0.28 q,t.

EXAMPLE 16 1,3-Dimethyl-2-diethylaminoimidazolidinium tetrafluoroborate

8.77 g (42.6 mmol) of 1,3-dimethyl-2-diethylaminoimidazolidinium chloride are initially introduced in a PFA flask. 4.76 g (236.8 mmol) of anhydrous hydrofluoric acid are added over the course of 3 min with vigorous stirring and cooling using an ice bath. The reaction mixture is stirred with ice-bath cooling for a further 20 min, and then 6.35 g (44.7 mmol) of boron trifluoride etherate are added over the course of 5 min while the reaction mixture is stirred vigorously using a magnetic stirrer. The reaction mixture is stirred at room temperature for a further hour, and then all volatile components of the mixture are removed under reduced pressure. The residue is dried at 90-105° C. in an oil bath for two hours under a vacuum of 1.3 Pa, giving 9.17 g of a crystalline material (m.p. 58-60° C.). The yield of 1,3-dimethyl-2-diethylaminoimidazolidinium tetrafluoroborate is 88.7%, based on 1,3-dimethyl-2-diethylaminoimidazolidinium chloride.

¹⁹F NMR (reference: CCl₃F—internal standard; solvent: CD₃CN): −150.42 s; −150.47 s (BF₄ ⁻).

¹H NMR (reference: TMS; solvent: CD₃CN): 1.19 t (2CH₃); 2.94 s (2CH₃); 3.34 q (2CH₂); 3.68 (2CH₂); ³J_(H,H)=7.1 Hz.

EXAMPLE 17

The viscosities of the guanidinium compounds, listed in Table 1, are measured on an SVM3000 viscometer from Anton Paar, Austria, using the standard procedure described in the manual accompanying the viscometer. TABLE 1 Viscosity data Viscosity, cP (mPa · s) Compound at 20° C. 40° C. 60° C. 80° C. 1,3-Dimethyl-2- 376 107 43 21 dibutylaminoimida- zolidinium tris(penta- fluoroethyl)- trifluorophosphate 1,3-Dimethyl-2- 78 34 18 diethylaminoimida- zolidinium tris(penta- fluoroethyl)- trifluorophosphate N,N,N′,N′- 164 57 27 15 Tetramethyl-N″-ethyl- guanidinium tris(penta- fluoroethyl)- trifluorophosphate N,N,N′,N′- 47 22 13 8 Tetramethyl-N″,N″- diethylguanidinium tetracyanoborate Comparative 346 (25° C.) 269 124 substance 5d (Green Chem. 2003, 5, 347-352): N,N-dimethyl- N′,N′,N″,N″-tetra- hexylguanidinium bis(trifluoro- methanesulfonyl)imide 

1. Salt having a guanidinium cation which has the general formula (1)

in which R═H straight-chain or branched alkyl having 1-20 C atoms, or in the case of A⁻=[(C₂F₅)₃PF₃]⁻ straight-chain or branched alkyl having 2-20 C atoms or saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, in particular phenyl, which may be substituted by alkyl groups having 1-6 C atoms, where the R are in each case identical or different, where up to four R may be connected to one another in pairs by a single or double bond, where one or more R may be partially or fully substituted by halogens, in particular-F and/or —Cl, or partially by —CN or —NO₂, and where one or two non-adjacent carbon atoms of the R may be replaced by atoms and/or atom groups selected from the group —O—, —C(O)—, —C(O)O—, —S—, —S(O)—, —SO₂—, —SO₂—, —N═, —N═N—, —NH—, —NR′—, —PR′—, —P(O)R′—, —P(O)R′—O—, —O—P(O)R′—O—, —P(O)(NR′₂)—NR′— and —PR′₂═N—, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl or an unsubstituted or substituted heterocycle, and A⁻ is selected from the group consisting of: [(FSO₂)₂N]⁻, [R^(F)CF₂SO₃]^(—), [(R^(F′)SO₂)₂N]⁻, [(R^(F′)SO₂)₃C]⁻, [(FSO₂)₃C]⁻, [R^(F)CF₂C(O)O]⁻, [P(C_(n)F_(2n+1-m)H_(m))_(y)F_(6-y)]⁻, [P(C₆F₅)_(y)F_(6-y)]⁻, [R^(F) ₂P(O)O]⁻, [R^(F)P(O)O₂]²⁻, [BF_(z)R^(F) _(4-z)]⁻, [BF_(z)(CN)_(4-z)]⁻, [N(CF₃)₂]⁻, [N(CN)₂]⁻, [C(CN)₃]⁻ or

where R^(F)=perfluorinated and straight-chain or branched alkyl having 1-20 C atoms, preferably having 1-12 C atoms, perfluorinated and straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, perfluorinated and straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, perfluorinated and saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, in particular phenyl, which may be substituted by perfluoroalkyl groups, where a plurality of R^(F) may in each case be identical or different, where the R^(F) may be connected to one another in pairs by a single or double bond,and where one or two non-adjacent carbon atoms of the R^(F) which are not in the a-position to the heteroatom may be replaced by atoms and/or atom groups selected from the group —O—, —SO₂— and —NR′— or by the end group —SO₂X′, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl, including —C₆F₅, or an unsubstituted or substituted heterocycle, and X′=F, Cl or Br, and R^(F′)=perfluorinated and straight-chain or branched alkyl having 2-20 C atoms, perfluorinated and straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, perfluorinated and straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, perfluorinated and saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, in particular phenyl, which may be substituted by perfluoroalkyl groups, where a plurality of R^(F′) may in each case be identical or different, where the R^(F′) may be connected to one another in pairs by a single or double bond, and where one or two non-adjacent carbon atoms of the R^(F′) which are not in the a-position to the heteroatom may be replaced by atoms and/or atom groups selected from the group —O—, —SO₂— and —NR′— or by the end group —SO₂X′, where R′=unfluorinated, partially or perfluorinated C₁- to C₆-alkyl, C₃- to C₇-cycloalkyl, unsubstituted or substituted phenyl, including —C₆F₅, or an unsubstituted or substituted heterocycle, and X′=F, Cl or Br, n=1 to 20, preferably 1 to 12, and m=0, 1, 2 or 3 and y=1, 2, 3 or 4 and z=0, 1, 2 or 3 and —X— and —Y— are in each case identical or different and denote —C(O)—C(O)—, —C(O)—(CH₂)_(q)—C(O)—, where q=1, 2 or 3, —C(O)—(CF₂)_(q)—C(O)—, where q=1, 2 or 3, —C(CF₃)₂—C(CF₃)₂—,

where k=1, 2, 3 or 4 and p=1 or
 2. 2. Salt according to claim 1, characterised in that R is hydrogen and/or a straight-chain or branched alkyl having 1-12 C atoms.
 3. Salt according to claim 2, characterised in that R is selected from the group methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, phenyl and cyclohexyl.
 4. Salt according to claim 1, characterised in that at least two substituents R are connected to one another by single or double bonds in such a way that a monocyclic cation is formed.
 5. Salt according to claim 1, characterised in that A⁻ is selected from the group [(FSO₂)₂N]⁻, [CF₃CF₂SO₃]⁻, [(C₂F₅SO₂)₂N]⁻, [(C₂F₅SO₂)₃C]⁻, [(FSO₂)₃C]⁻, [CF₃CF₂C(O)O]⁻, [P(C₂F₅)₃F₃]⁻, [P(CF₃)₃F₃]⁻, [P(C₂F₄H)(CF₃)₂F₃]⁻, [P(C₂F₃H₂)₃F₃]⁻, [P(C₂F₅)(CF₃)₂F₃]⁻, [P(C₆F₅)₃]⁻, [P(C₃F₇)₃F₃]⁻, [P(C₄F₉)₃F₃]⁻, [P(C₂F₅)₂F₄]⁻, [(C₂F₅)₂P(O)O]⁻, [(C₂F₅)P(O)O₂]²⁻, [P(C₆F₅)₂F₄]⁻, [(CF₃)₂P(O)O]⁻, [(C₄F₉)₂P(O)O]⁻, [CF₃P(O)O₂]²⁻, [BF₃(CF₃)]⁻, [BF₂(C₂F₅)₂]⁻, [BF₃(C₂F₅)]⁻, [BF₂(CF₃)₂]⁻, [B(C₂F₅)₄]⁻, [BF₃(CN)]⁻, [BF₂(CN)₂]⁻, [B(CN)₄]⁻, [B(CF₃)₄]⁻, [N(CF₃)₂]⁻, [N(CN₂)₂]⁻, [C(CN)₃]⁻, or


6. Process for the preparation of a salt according to claim 1, characterised in that a guanidine (NR₂)₂C═(NR) or a guanidinium salt C(NR₂)₃ ⁺ X⁻, where X⁻ is selected from the group F⁻, Cl⁻, Br⁻, I⁻, [HF₂]⁻, [CN]⁻, [SCN]⁻, [CH₃COO]⁻, [CF₃COO]⁻, [CF₃SO₃]⁻, [CH₃OSO₃]⁻, [SiF₆]²⁻, [BF₄]⁻, [SO₄]²⁻, [NO₃]⁻, tosylates, malonates, substituted malonates and [CO₃]⁻, is reacted with an acid AH or a salt Kt⁺ A⁻, where A and the radicals R are as defined in claim 1, and Kt is an alkali or alkaline earth metal.
 7. Process for the preparation of a salt according to claim 1, characterised in that a guanidine (NR₂)₂C═(NR) or a guanidinium salt C(NR₂)₃ ⁺ X⁻, where X⁻ is selected from the group F⁻, Cl⁻, Br⁻, I⁻, [HF₂]⁻, [CN]⁻, [SCN]⁻, [CH₃COO]⁻, [CF₃COO]⁻, [CF₃SO₃]⁻, [CH₃OSO₃]⁻, [SiF₆]²⁻, [BF₄]⁻, [SO₄]²⁻, [NO₃]⁻, tosylates, malonates, substituted malonates and [CO₃]⁻, is reacted with an ester AR, where A and the radicals R are as defined in claim 1, but where perhalogenated alkyl groups having 1-20 C atoms, cycloalkyl groups having 3-7 C atoms, alkenyl groups having 2-20 C atoms and alkynyl groups having 2-20 C atoms are excluded for the substituents R, and Kt is an alkali or alkaline earth metal.
 8. Process according to claim 6, characterised in that the reaction is carried out at a temperature at which at least one of the components is liquid.
 9. Process according to one or more of claim 6, characterised in that the reaction is carried out in a polar solvent, in a nonpolar solvent or without a solvent.
 10. Process according to claim 6, characterised in that the reaction of the reagents is carried out with an up to five-fold excess of one of the reactants, preferably in equimolar amount.
 11. Process for the preparation of a guanidinium salt of the formula I where A⁻ denotes [BF₄]⁻, characterised in that firstly guanidinium chloride C(NR₂)₃ ⁺ Cl⁻ or guanidinium bromide C(NR₂)₃ ⁺ Br⁻, where the radicals R are as defined in claim 1, is reacted with anhydrous HF, and the guanidinium fluoride formed in situ is subsequently reacted with boron trifluoride etherate BF₃*Et₂O.
 12. Process according to claim 11, characterised in that the reaction is carried out at a temperature at which at least one of the components is liquid.
 13. Process according to claim 11, characterised in that the reaction is carried out with an up to 10% excess or preferably with an equimolar amount of boron trifluoride etherate in relation to the guanidinium salt.
 14. Use of a salt of the general formula (1)

in which the radicals R and the anion A are as defined in claim 1, as ionic liquid. 